Effects of low melting point materials on sinterability and microwave dielectric properties of X₂SiO₄–CaTiO₃ (X = Mg, Zn) for LTCC

The effect of adding different low melting point compounds on the crystalline phases, microstructure and microwave dielectric properties of the X₂SiO₄–CaTiO₃ (X = Mg, Zn) ceramics was compared. The 0.91Mg₂SiO₄–0.09CaTiO₃ samples doped with 15.0–35.0 wt% ZB glass were unsintered at 950 °C for 3 h in air. The grains were denser, as the 0.91Mg₂SiO₄–0.09CaTiO₃ samples were doped with 12.0 wt% BLB and the 0.95Zn₂SiO₄–0.05CaTiO₃ samples were doped with 4.0 wt% LB or 7.0 wt% BLB at 950 °C for 3 h in air. Adding 2.0–6.0 wt% LB to the 0.95Zn₂SiO₄–0.05CaTiO₃ ceramics, the sintering temperature was lowered to 950 °C, the relative density values of the ceramics were more than 90 %, and the Q × f values were more than 18,000 GHz (f = 7.1 GHz). However, the 0.91Mg₂SiO₄–0.09CaTiO₃ ceramics doped with 4.0–8.0 wt% LB were not dense, and the Q × f values were lower than 6500 GHz (f = 7.1 GHz) at 950 °C for 3 h. For the 0.95Zn₂SiO₄–0.05CaTiO₃ ceramics doped with 6.5–8.5 wt% BLB and the 0.91Mg₂SiO₄–0.09CaTiO₃ ceramics doped with 10.0–14.0 wt% BLB, the relative density of the two kinds of the ceramics can reach to 94 %, and the maximum Q × f values of the ceramics were both more than 11,000 GHz (f = 6.1 GHz).